For example, in the following Patent document 1, it is aimed “to prevent surely a cross rolling to improve a maneuvering stability furthermore, and exclude a different feeling given to vehicle passengers”, and there is proposed “a roll damping force control apparatus for a vehicle with damping force generating mechanisms for generating a damping force proportional to a roll velocity of the vehicle body, and capable of varying the roll velocity, provided between front and rear wheels and a vehicle body separately, wherein front and rear roll damping force control means is provided for controlling the damping force generating mechanisms respectively, so as to increase a ratio of the damping force of the front wheel to that of the rear wheel, as the value detected by the steering angle velocity detecting means for detecting the steering angle velocity increases”. And, a structural example is disclosed in FIG. 2, and it is explained at the left below section of page 3 of its publication that “with respect to each of front wheels and rear wheels, an upper cylinder chamber U of a left wheel oil pressure cylinder 20FL (20RL) is coupled to a lower cylinder chamber L of a right wheel oil pressure cylinder 20FR (20RR) through one oil pressure piping 26A, and the lower cylinder chamber L of the left wheel oil pressure cylinder 20FL (20RL) is coupled to the upper cylinder chamber U of the right wheel oil pressure cylinder 20FR (20RR) through the other oil pressure piping 26B, whereby the cylinders are coupled crossly to each other”, and it is explained at the right below section of the same page that “a control section 14B comprises a roll damping controller 36 which controls damping coefficients Ct, Cr for variable throttle valves 22F, 22R, and a steering angle sensor 38 and a vehicle speed sensor 40 which send detected signals to the controller 36”.